Power scaling of fiber lasers and amplifiers typically requires large-mode-area (LMA) fibers in order to reduce intensity and avoid non-linear effects. To increase mode area, the core size must typically be enlarged. However, increased mode area and core size is frequently accompanied by the generation and/or transmission of higher order modes, which can significantly reduce the quality of the output beam of the fiber. Thus, single-mode operation of conventional fibers can become impractical as core size increases. Accordingly, improvements to optical fibers are desirable.